Systems comprising at least one autogenerator, in particular of the free piston type, and a receiver machine driven by the power gases supplied by the auto-generator



June 1964 H. HORGEN SYSTEMS COMPRISING AT LEAST ONE AUTO-GENERATOR, IN PARTICULAR OF THE FREE PISTON TYPE, AND A RECEIVER MACHINE DRIVEN BY THE POWER GASES SUPPLIED BY THE AUTO-GENERATOR 2 Sheets-Sheet 1 Filed Jan. 9, 1962 $10 J 13 t j M I a?? 4 I] v Y J lNVE/VTOR 65/ 15 l aryn/ BY I; I M4* ATTORNEY)" June 9, 1964 H. HORGEN 3,136,118

SYSTEMS COMPRISING AT LEAST ONE AUTO-GENERATOR, IN PARTICULAR OF THE FREE PISTON TYPE. AND A RECEIVER MACHINE DRIVEN BY THE POWER GASES SUPPLIED BY THE AUTO-GENERATOR Filed Jan. 9, 1962 2 Sheets-Sheet 2 N VE N TOR fi /y; A a ryr/v Arm/ww United States Patent SYSTEMS COMPRESING AT LEAST ONE AUTO- GENERATQR, IN PARTICULAR OF THE FREE PISTON TYPE, AND A CEIVER MACHTNE DRIVEN BY THE POWER GASES SUPPLIED BY THE AUTO-GENERATOR Helge Horgen, Lyons, France, assignor to Societe dEtudes et de Participations Eau, Gaz, Electricite, Energie, S.A., Geneva, Switzerland, a society of Switzerland Filed Jan. 9, 1%2, Ser. No. 165,209 Claims priority, application France Jan. 11, 1961 4 Glairns. (Cl. 6013) The present invention relates to a system comprising at least one auto-generator, in particular of the free piston type, and a receiver machine, preferably a turbine, driven by the power gases supplied by the auto-generator. The invention is more particularly, but not exclusively, concerned with systems of this kind where the auto-generator compresses air in its compressor portion during the return strokes of the free pistons, i.e., during the strokes for which compression takes place in the power cylinder of the auto-generator.

The chief object of this invention is to provide a system of this kind which is better adapted to meet the requirements of practice than those known up to this time and in particular which has a higher yield.

This invention consists chiefly in causing, during every period for which the compressor piston delivers compressed air from the compressor cylinder to a receiver connected to the inlet of the power cylinder, said compressor piston to force air through a conduit which bypasses the power cylinder of the auto-generator and preferably also the casing which contains compressed air for scavenging and feeding said power cylinder, this by-passed air being led either to a space, located downstream of said power cylinder, where this by-passed air mixes with the hot gases under pressure coming from said power cylinder, or directly to the receiver machine, which is generally a turbine.

Preferred embodiments of this invention will be hereinafter described with reference to the appended drawings given merely by way of example and in which:

FIG. 1 shows diagrams illustrating the operation of the compressor portion of the auto-generator.

FIG. 2 shows in longitudinal section an embodiment of a system according to the present invention.

FIG. 3 shows another embodiment of a system according to this invention, this system comprising several autogenerators.

FIGS. 4, 5 and 6 are views partly in section, showing three other embodiments of the invention, respectively.

It should be noted that the yield of a free piston autogenerator of conventional type is often reduced due to important losses in the air-cycle. These losses are generally due to the fact that the whole of the air compressed and delivered by the compressor portion of the auto-generator is made to how through the. power cylinder of the autogenerator so as to work as scavenging air. No such an amount of air is necessary for scavenging so that compressed air is thus wasted. Furthermore, due to the fact that the whole of the air compressed in the compressor portion of the auto-generator is delivered into the casing which surrounds the power cylinder and which constitutes a reservoir for scavenging and feed air, there is produced, during every delivery period, an unnecessary rise of the pressure in this casing and consequently a corresponding increase of the pressure at the delivery of the compressor portion, which increases the compression work to be supplied by the auto-generator power portion, and this without any advantage. This increase of the pressure in the compressed air casing is particularly important in autogenerators where compression and delivery of air from 3,136,] 18 Patented June 9, 1964 the compressor portion take place while the free pistons are moving in the power cylinder on their compression strokes, i.e., when the feed and exhaust openings of the power cylinder are closed.

In order to avoid these drawbacks, according to the present invention, during the delivery strokes of the compressor portion of the auto-generator, a portion of the compressed air is made to fiow through a conduit which bypasses the power cylinder of the auto-generator and also the casing that contains compressed air for scavenging and feeding said power cylinder, this by-passed air being led either to a space, located downstream of the power cylinder, where the by-passed air mixes with the hot gases under pressure coming from the power cylinder (and which contain the combustion gases formed in this cylinder) or directly to the receiver machine, which generally consists of a turbine. This arrangement considerably reduces the compression work to be performed in the auto-generator. The by-passing of the whole or nearly whole of the air should take place during the relatively short periods for which air is delivered from the compressor portion.

It seems that the best construction to obtain this result consists in causing a portion of the air to pass from the compressor to the exhaust reservoir of the auto-generator, or even directly to the receiver machine, through check valves of the type generally employed for the delivery of air to the casing which contains the air for scavenging and feeding the power cylinder. Thus it is obtained that the by-passing of a portion of the air takes place automatically without any special control during the short delivery periods of the compressor. The ratio between the two air streams, to wit that flowing to the compressed air casing and that which is by-passed, is determined by the ratio between the respective cross-sections of, on the one hand, the check valves which control the communication between the compressor portion and the compressed air casing and, on the other hand, the check valves through which the by-passed stream is made to flow. It is therefore possible, by a suitable choice of this ratio, to determine at will the amount of air that is by-passed.

This construction further has the advantage that it lowers the pressure in the compressor portion so that this pressure becomes nearer to that existing downstream of the power cylinder, before the free piston or pistons reach the end of the stroke during which air compression and delivery take place. Due to the great dead space of the compressor portion of a free piston machine, this lowering of the pressure in the compressor cylinder or cylinders before the beginning of the expansion and suction stroke in these cylinders involves a considerable increase of the volumetric efficiency of the compressor portion of the auto-generator. This lowering of the pressure in the compressor cylinder or cylinders is due to the fact that the speed of the free piston or pistons when they come close to their inner deadcenter positions decreases considerably, so that the air delivered at the end of the delivery stroke can escape entirely without too great pressure drops past the valves through which the by-passed air is sent to aspace, located downstream of the power cylinder, where the pressure is substantially lower than in the compressed air casing. Consequently the valves through which the compressor cylinder communicate with the compressed air casing'close before the piston or pistons reach the end of their delivery stroke. Of course the choice of the pressure thus obtained at the end of the delivery stroke in the compressor cylinder or cylinders depends upon the ratio to each other or the cross-section of the checkvalves serving to the delivery of air to the compressed air casing and of the check valves serving to the delivery of air to be by-passed. Another advantage of this reduction of the pressure in the compressor portion before the greater than that admitted up to now, which reduces the pressure drops and further increases the yield.

The diagrams of FIG. 1 illustrate these facts.

FIG. 1 shows in solid lines, a diagram where the longitudinal displacements c of the piston are plotted in abscissas and the pressures p are plotted in ordinates, in a compressor cylinder of a conventional auto-generator wherein compression takes place during every return stroke of a compressor piston, i.e., during the strokes that coincide with the compression strokes of the power piston in its cylinder, this compressor piston delivering, at the end of this return stroke, compressed air directly into a casing that surrounds the power cylinder. The compression stroke begins at point A and compression without delivery of air goes on until point B. At this time takes place the opening of the delivery check-valves which serve to connect the compressor cylinder with the compressed air casing where the existing pressure is minimum. Thencompressed air is delivered into said casing where due to the fact that no air can flow out, the pressure rises to a point C which indicates at the same time the end of the compression and delivery stroke of the compressor piston. As soon as the compressor piston starts on its outward stroke, i.e., that corresponding to the power stroke of the'power piston, the pressure in the compressor cylinder drops down to D and a fresh air charge is admitted during the portion DA of this outward stroke of the compressor piston. If on the contrary a portion of the compressed air is made to flow directly from the compressor cylinder into the exhaust reservoir located downstream of the power cylinder, there is obtained a diagram such as indicated partly by the dotted lines of FIG. 1. Air compression begins in this case also at point A but it goes on only as far as point B corresponding to a pressure slightly lower than that coresponding to point B. This is due to the fact that the pressure in the compressed air casing, according to the invention, varies at a level lower than that indicated by curve BC. During the period of delivery of compressed air, the pressures in the compressed air casing vary as indicated by curve B C C This is due to the fact that during the first portion of the delivery period, compressed air is delivered into the compressed air casing, but the rise of the pressure in this casing is slower than in the preceding case because a portion of the air, instead of being delivered into said casing, is made to flow through the by-pass means directly to said exhaust reservoir. Before the end of the delivery stroke of the compressor pistons, i.e., at point C due to the slowing down of the movement of the compressor piston, the delivery check valves which establish communication with the compressed air casing are closed and the whole of the remainder of the compressed air flows through the by-pass conduit. Owing to the fact that the pressure existing in the exhaust reservoir, downstream of the power cylinder, is substantially lower than the pressure existing in the compressed air casing, the pressure in the compressor cylinder drop, at the end of the delivery period, down to the pressure corresponding to point C this last mentioned pressure being slightly higher than the pressure existing in the exhaust reservoir. From the beginning of the next stroke of'the compressor piston, expansion in the compressor cylinder takes place along a line C D which permits, subsequently, a suction along path D A which is substantially longer than path DA so that the volumetric efiiciency of the compressor cylinder is improved. This efliciency may be further improved by dimensioning the by-pass means in such manner that the pressure wave in said means produces, when the compressor piston is at the end of its delivery stroke, a minimum of pressure in the vicinity of, the starting end of said means, i.e., in the d vicinity of the delivery check valve belonging thereto. Thus the compressor cylinder is relieved from a still more important portion of the air contained at this time in its dead space.

FIG. 2 shows at I an auto-generator having opposed free pistons and at II an exhaust reservoir which receives the power gases supplied by this auto-generator, which gases serve to drive a gas turbine III.

Auto-generator I comprises, in conventional fashion, a power cylinder 1 in which are slidably mounted two pistons 2 having opposed reciprocating movements. These pistons 2 are rigid with respective compressor 3 thus forming two opposed free pistons the movements of which are synchronized by a mechanism of a well-known type not shown by the drawing.

' The power portion, consisting of cylinder 1 and pistons 2, work as a two-stroke'diesel internal combustion engme.

The compressor portion of the auto-generator comprises pistons 3 slidable in two compressor cylinders 4 disposed on opposite sides of power cylinder 11, each of these compressor cylinders 4 being divided, by its compressor piston 3, into two chambers 4,, and 4 The inner chamber 4 constitutes the compressor cylinder proper, whereas the outer cylinder 4;, constitutes a return pneumatic energy accumulator intended to produce the return strokes (i.e., the inward strokes) of the free pistons 2-3. The outward strokes of these pistons are produced by the combustion of fuel in cylinder 1. This last mentioned cy1- inder, which is provided with one or several fuel injectors, not shown, comprises inlet openings 5 for the feed and scavenging air stored under pressure in compressed air casing 6, which surrounds power cylinder 1, this casing thus acting as an air reservoir. Furthermore, cylinder 1 V is provided with outlet openings 7 through which the inside of cylinder 1 may communicate with a sleeve 8 surrounding these outlet openings 7 and separating them from the inside of casing 6, this sleeve 8 opening into the exhaust reservoir II. These openings 5 and 7 are controlled by pistons 2 themselves, which open them when the free pistons are getting close to their outer dead center positions.

Each of the chambers 4,, is provided with one or several suction valves 9 and with a plurality of delivery valves. These delivery valves are divided into two groups, 10 and N respectively. Valves 10 ensure, during the period of delivery of compressed air from chambers 4 the communication between said chambers and the inside of casing 6, whereas check-valve 10 ensures a communication between said chambers 4 and exhaust reservoir II. Therefore during every period for which the compressor piston 3 delivers compressed air from chambers 4,, there is obtained, in each of these chambers, a curve of the pressures corresponding to that indicated at AB -C C D A in FIGURE 1.

Preferably, as shown by FIG. 2, the by-pass conduit, i.e., the conduit which conveys the air that has flown past check-valve 10 toward reservoir II, is disposed in the interior of easing 6, and isformed, for example, by ducts 11,, and lli which connect the sleeve 8 to the places where the by-passed part of the compressed air leaves compartments 4 The arrangement of the pipe 11 11 in the interior of the casing 6 makes it possible to dispense with complete gas-tightness of this pipe, which not only simplifies the construction, but also has the effect that, in the periods during which there is'no delivery of air from the compartments 4,, the by-pass conduit is scavenged by leakage air from casing 6, so that exhaust soot is kept away from the valves 10 The by-pass conduit may, of course, alternatively extend outside the casing 6. In that case, it must be gas tight but, on the other hand, in a plant comprising a number of auto-generators feeding a turbine or other receiver machine, it is thereby possible to combine the by-pass conduits of all the auto-generators and to form a compressed air system in parallel with the usual system containing the power gas which includes. the combustion gases of the power cylinders of the auto-generators.

Such a plant is shown in FIG. 3.

This plant comprises three generators 1 1 1 the compressor portions of which are arranged as described hereinbefore for the compression portion of the autogenerator shown in FIG. 2 that is to say a part of the air, during every delivery stroke of the compressor pistons, is delivered to the casing 6 of each auto-generator and serves as feeding and scavenging air for the power cylinders of these auto-generators, while another part of the compressed air, during every delivery stroke of the compressor pistons is delivered, to a by-pass conduit denoted by 12 in FIG. 3. The exhaust collectors 11 11 and II of the auto-generators are connected together by a pipe 13 leading hot power gas under pressure to the gas turbine 14. Pipe 13 includes a combustion chamber 15 into which fuel is injected, for example by means of one or more injectors 16.

The by-pass air flowing through conduit 12, is also led to said combustion chamber 15 after passing through a heating device 17, where it is heated by the residual heat contained in the exhaust gases of the turbine 14, these gases being led to the said device 17 by a pipe 18-.

Of course, the by-passed air passing through conduit 12 could also be utilized in some other way, more particularly in any plants where there is need of air under pressure free from combustion gas. If necessary, the by-passed air may be cooled. If the pressure of the bypassed air is relatively low, there is obtained a still more considerable discharge of the dead spaces of the compressor cylinders at the moment at which the compressor pistons reach their inner dead point, which results in a very good volumetric efliciency of the compressor cylinders.

The auto-generators of the plants shown in FIGS. 2 and 3 are auto-generators in which the compression lof the air and its delivery from the compressor cylinders occur during the return stroke of the pistons, that is to say during the stroke towards their inner dead point. The invention is also advantageously applicable, however, in plants where the generator or generators compress and deliver air during the stroke of the pistons towards their outer dead points, because even in this case the application of the invention makes it possible to reduce the scavenging losses of the engine. The same applies to plants having twin generators, in which the pistons compress and deliver air from the compressor portion of each auto-generator during the return stroke. By twinning of two auto-generators, is here understood the combination of two auto-generators of this kind, in which the compressed air casings are in communication with each other, so that at least during part of the delivery period of the compressed air from the compressor portion of one of these auto-generators, the inlet and exhaust ports of the power cylinder of the power cylinder of the other autogenerator are open, whereby it is possible to utilize immediately part of the air delivered by one of the autogenerators in the other auto-generator.

If the present invention is applied to such twin engines, it is advantageous to direct the by-passed part of the compressed air from the compressor portion of one of the auto-generators to the exhaust collector of the other auto-generator.

Where there is an excess of scavening air only over a range of lower loads, for example up to about /3 of full load, means operated in dependence upon the load may be provided for automatically closing the valves 10,, when the loads exceed a predetermined value.

FIG. 4 shows a modification where each compressor unit is divided into two parts one of which delivers air under pressure into reservoir II through a conduit 21 whereas the other one delivers air under pressure into casing 6, possibly at a lower pressure, which reduces the total compression work.

This result is obtained by making use of a stepped piston 3 3 Piston element 3 works in a compression chamber 4 delivering air into conduit 21 past valve 10 Piston element 3 works in a compression chamber 4 from which air is delivered into casing 6 past valves 10 Air is admitted into said chambers 4 4 by means of check-valves 9 and 9 respectively.

In the modification of FIG. 5, the left hand compressor unit delivers compressed air into casing 6 in conventional fashion.

The compression chamber 4 of the right hand compressor unit is separated from casing 6 by a partition 22, thus forming a separate chamber 23. This chamber 23 communicates through a conduit 24 with the pipe leading from reservoir I to turbine 11 so that this compressor portion 4,, feeds compressed air directly to turbine III.

In the embodiment of the present invention illustrated in FIG. 6, casing 6 communicates with reservoir H through a conduit 25. In this conduit is mounted a slide-valve 26. Slide valve 26 is controlled by two pistons 27 and 28 acting in opposition to each other. Piston 27 is subjected to the pressure in air compressor cylinder 4,. Piston 28 is subjected to the pressure in compressed air casing 6, to which is added the thrust-of a spring 29 (intended to compensate for the pressure drops past check-valves 10). Slide valve 26 opens only during the portions of the movement of compressor pistons 3 for which air flows from space 4 into casing 6.

What I claim is:

1. A system which comprises, in combination,

at least one auto-generator of power gases under pressure, which auto-generator comprises:

a power portion of the internal combustion piston engine type comprising a power cylinder and a power piston mounted to cooperate therewith, said power cylinder having an inlet for scavenging and combustion air and an exhaust gas outlet,

an air compressor portion comprising a compressor cylinder and a compressor piston mounted to cooperate with said compressor cylinder, said compressor piston being operatively connected with said power piston so as to be driven by it,

a compressed air casing connected to said inlet,

and means for feeding compressed air from said compressor cylinder to said casing, said last mentioned means including check valve means,

a gas turbine having its input connected with said exhaust gas outlet,

and means for conveying compressed air from said compressor cylinder to said turbine input, said last mentioned means being arranged to by-pass both said compressed air casing and said internal combustion engine, said last mentioned means including check valve means between said compressor cylinder and said turbine input.

2. A system which comprises, in combination,

at least one auto-generator of power gases under pressure, which auto-generator comprises:

a power portion of the internal combustion engine type comprising at least one power cylinder and one power piston mounted to cooperate therewith, said power cylinder having an inlet and an outlet,

a compressed air casing connected to said power cylinder inlet to feed air under pressure thereto for scavenging and air feed of said power cylinder,

an air compressor portion comprising one compressor cylinder and one compressor piston mounted to cooperate therewith, said compressor piston being operatively connected with said power piston so as to be driven by it,

and means for feeding compressed air from said compressor cylinder to said compressed air casing during every working stroke of said compressor piston a gas turbine having its input connected with said power cylinder outlet to receive the exhaust gases therefrom, i i

and means for conveying to said gas turbine input a portion of the air compressed in said compressor cylinder during every stroke portion of said compressor piston for which it'delivers air from said compressor cylinder to said compressed air casing, said air conveying means being arranged to bypass both said compressed air casing and said power cylinder.

3. A system according to claim 2 wherein said meansfor feeding compressed air from said compressor cylinder to said compressed air casing comprise check valve means interposed between said compressor cylinder and said compressed air casing and the means for conveying air from said compressor cylinder to said gas turbine input comprise by-pass conduit means leading to said gas turbine and check valve means interposed between said compressor cylinder and said by-pass conduit means and opening toward said conduit.

4. A system according to claim 3 wherein said by-pass conduit means comprises a conduit located inside said compressed air casing, said second mentioned check valve means opening directly into said conduit and said conduit being in direct communication with said gas turbine input.

References (Iited in the file of this patent UNITED STATES PATENTS 2,139,425 Steiner Dec. 6, 1938 2,292,288 Pateras Pescara Aug. 4, 1942 2,439,473 Kalitinsky Apr. 13, 1948 3,016,689 Bayer et a1. Jan. 16, 1962 

1. A SYSTEM WHICH COMPRISES, IN COMBINATION, AT LEAST ONE AUTO-GENERATOR OF POWER GASES UNDER PRESSURE, WHICH AUTO-GENERATOR COMPRISES: A POWER PORTION OF THE INTERNAL COMBUSTION PISTON ENGINE TYPE COMPRISING A POWER CYLINDER AND A POWER PISTON MOUNTED TO COOPERATE THEREWITH, SAID POWER CYLINDER HAVING AN INLET FOR SCAVENGING AND COMBUSTION AIR AND AN EXHAUST GAS OUTLET, AN AIR COMPRESSOR PORTION COMPRISING A COMPRESSOR CYLINDER AND A COMPRESSOR PISTON MOUNTED TO COOPERATE WITH SAID COMPRESSOR CYLINDER, SAID COMPRESSOR PISTON BEING OPERATIVELY CONNECTED WITH SAID POWER PISTON SO AS TO BE DRIVEN BY IT, A COMPRESSED AIR CASING CONNECTED TO SAID INLET, AND MEANS FOR FEEDING COMPRESSED AIR FROM SAID COMPRESSOR CYLINDER TO SAID CASING, SAID LAST MENTIONED MEANS INCLUDING CHECK VALVE MEANS, A GAS TURBINE HAVING ITS INPUT CONNECTED WITH SAID EXHAUST GAS OUTLET, AND MEANS FOR CONVEYING COMPRESSED AIR FROM SAID COMPRESSOR CYLINDER TO SAID TURBINE INPUT, SAID LAST MENTIONED MEANS BEING ARRANGED TO BY-PASS BOTH SAID COMPRESSED AIR CASING AND SAID INTERNAL COMBUSTION ENGINE, SAID LAST MENTIONED MEANS INCLUDING CHECK VALVE MEANS BETWEEN SAID COMPRESSOR CYLINDER AND SAID TURBINE INPUT. 